A typical apparatus for dispensing a heated liquid, such as hot melt adhesive, generally includes a dispensing module having a valve element that opens and closes a dispensing outlet. The valve element is positioned within a passage supplied with pressurized liquid and contacts a valve seat to prevent the adhesive from flowing to the outlet. To dispense the adhesive, an actuator, such as an electrically and/or pneumatically operated actuator, causes the valve element to move away from the valve seat and allows the adhesive to flow from the passage to the outlet. A biasing mechanism, such as a spring, or the same actuator may then cause the valve element to move back toward the valve seat to close the outlet.
Various arrangements have been developed for heated liquid dispensers. For example, U.S. application Ser. Nos. 10/975,227 (“the '227 application”) and 10/907,514 (“the '514 application”), the disclosures of which are fully incorporated herein by reference, relate to dispensers in which a pivot arm operatively connects the valve element in a dispensing module to a piston in an adjacent housing. The piston is maintained in a first position within the housing by a spring or air pressure so that the pivot arm forces the valve element against a valve seat. A liquid supply component (typically referred to as a manifold) is coupled to the dispensing module on an opposite side from the housing and supplies heated liquid to a fluid passage around the valve element. Thus, when the piston member moves down, the pivot arm causes the valve element to move away from the valve seat so that the liquid within the fluid passage flows to an outlet.
Various areas for improvement exist, such as reducing complexity and increasing reliability of the actuating portion of the dispensing apparatus and reducing the size of the apparatus.